The structure, organization and development of the olfactory cortex will be studied with a variety of normal and experimental methods, including the autoradiographic and horseradish peroxidase method of demonstrating axonal connections, as well as the Golgi method and the electron microscope. By correlating the results obtained with these methods, an attempt will be made to characterize each neuron type and to define their interrelationships in one of the olfactory areas, the prepiriform cortex. The time course and pattern of development of the afferent axonal connections of this area will also be studied in neonatal rats, and the effect of partial deafferentation will be determined in both neonatal and adult rats.